The carbonyls of iron, nickel and cobalt have been the subjects of many patents covering both their preparation and their use. Such materials are usually prepared by reacting the pure metal or the metal sulfides, oxides, salts or esters with carbon monoxide, the latter reactions sometimes being effected in the presence of a reducing agent. See, for example, U.S. Pat. No. 2,473,993. Other known metal carbonyls include, for example, the various carbonyls of rhodium, tungsten, rhenium, osmium, iridium, molybdenum, ruthenium, chromium, vanadium and manganese as set forth on page 509 in Organometallic Chemistry, ACS Monograph No. 147, edited by H. Zeiss and published by Reinhold Publishing Corporation, New York, New York (1960). It appears that not all metals will form carbonyl derivatives. In addition, some metal carbonyls can only be formed from the pure metal while some metal carbonyls can only be formed from metal salts or esters. The very number of methods for preparing these compounds indicates the continuing search for improvement in such methods.
Known metal hydrocarbonyls include various hydrocarbonyls of chromium, molybdenum, tungsten, manganese, rhenium, iron, ruthenium, osmium, cobalt, rhodium, iridium and nickel as set forth on page 500 in Organometallic Chemistry supra. Cobalt hydrocarbonyl is described in U.S. Pat. No. 2,985,504 and is shown to be prepared by heating under pressure a mixture of cobalt octacarbonyl in a hydrocarbon solvent and carbon monoxide at pressure of about 1000 psig. at a temperature of about 110.degree.C., then adding to the pressurized system hydrogen gas to a molar ratio of hydrogen to carbon monoxide of 2:1, and then cooling the system to -70.degree.C. to produce a 70 percent yield of solid cobalt hydrocarbonyl. The prior art teaches the preparation of metal hydrocarbonyls starting with pure metal compounds to get pure metal products. Most prior art methods teach the use of such promoters or aids as copper and other catalysts, sulfur and certain hydrocarbons such as acetylene.
One of the principal objects of this invention is to provide a novel method for the preparation of pure metal hydrocarbonyls from impure starting products. Another object of this invention is to take advantage of the sensitivity to temperature and pressure of metal hydrocabonyls and to provide thereby a method of producing a pure metal powder from a metal oxide, metal sulfide, metal salt, metal ester and/or mixtures thereof by converting it or them to the corresponding metal hydrocarbonyl, isolating and reducing said metal hydrocarbonyl to pure metal while retrieving the hydrogen and carbon monoxide by-products. Another object is to provide a novel method for the separation of pure metals from mixtures of metals, metal oxides, metal sulfides, metals salts and/or metal esters by separately converting each of the mixture components which contain a given desired metal to the corresponding metal hydrocarbonyl, separating the hydrocarbonyl products from the rection system by simple conventional methods, preferably by simply drawing off gaseous products or sifting out solid products, and reducing each of the separated products to its respective pure metal. A particular object is to provide a method for the extraction and recovery of cobalt metal and nickel metal from ferronickel-type alloys. These objects as well as others which are apparent from the following description are satisfied by this invention in its various aspects.